Debris in the circulating coolant which collects or is trapped in fuel rod spacer grids is believed responsible for as many as 70% of known fuel rod failures. Laboratory and in-reactor experience indicate that fuel rod cladding failures can be caused by debris trapped in a grid region which reacts against the fuel rod cladding in a vibratory fashion resulting in rapid wear of the cladding. The size and shape of the debris capable of causing severe damage is quite variable and may include broken fuel assembly fasteners or other holddown spring assembly broken parts. Accordingly, it is desirable to be able to operate safely without reconstitution even if a part of the assembly breaks. This can be accomplished by retention of any potential debris.
U.S. Pat. No. 5,053,191 describes an improved fuel assembly holddown cantilevered spring and it and U.S. Pat. No. 4,792,429 show how the spring ends were designed to provide spring capture and retention in the unlikely event that a cantilever spring broke during operation. However, machining of these patents' leaves and capturing mechanisms are expensive and time consuming.